Effects of three growth regulators on selected characters in cotton

Abstract

A series of three 2-year experiments were conducted in cotton (Gossypium hirsutum L.) under irrigated and dryland conditions to study the effects of foliar applications of the growth regulators RH-531 and ethrel, ethrel alone, and O.C.B., respectively, with several seed treatments in the latter experiment. The first 2-year experiments included three concentrations of ethrel as a foliar application and four of RH-531 on 'Westburn' cotton. The second 2-year experiments studied 10 concentrations of ethrel as a foliar application on the same cultivar. In the last set of 2-year experiments studied on O.C.B., experiments were conducted in 1978 using eight cotton cultivars ('Westburn M', 'Tamcot SP21', 'Deltapine Land 16', 'Stoneville 213', 'Paymaster 303', 'Tamcot 788', 'Coker 5110', and 'Acala 1517E-l) and three seed treatments (none, tap water, and O.C.B). In 1979, two cotton cultivars (Westburn M and Stoneville 213), six seed treatments (four concentrations of O.C.B. vs. tap water vs. none), and two foliar applications (none vs. O.C.B.) were studied.

Analyses of RH-531 effects detected several significant differences, but no consistent positive trends were noted as concentration of the chemical changed. In addition, production of the compound has been discontinued by its manufacturer. For those reasons, it cannot be recommended for use as a foliar spray on cotton.

Ethrel in the first and second experiments affected several plant characters. At 5000 ppm, yield in several experiments was essentially zero. Therefore, that rate was omitted from these analyses. In 1975, 500 ppm of ethrel on dryland depressed plant height and lint yield; that rate increased T1 fiber strength in 1974-1975 on dryland. Plant height decreased significantly in 1977 at low rates under irrigation without significantly depressing lint yields. Application of low rates of ethrel may hold some promise where excessive plant height and vegetative growth cause problems under irrigation. Higher rates of application did depress yields considerably under irrigation even though slight increases in fiber length were noted. Yields were affected on dryland in 1977, but no consistent trends in that data were evident. Ethrel application may also be useful under those dryland conditions where fibers with low micronaires are commonly produced.

Analyses of O.C.B. experiments in 1978 indicate that neither seed treatments nor interactions of seed treatments with cultivars were significant for any character. In 1979, seed treatments were significant only for micronaire, but no obvious trends were detected for that trait. Foliar application of O.C.B. resulted in a slight increase in picked lint percent under irrigation. Seed treatment by cultivar interactions were detected for uniformity index and T1. Foliar application by cultivar interactions affected only T1. The second-order interaction affected plant height, uniformity index under irrigation, and micronaire under irrigation. O.C.B. either does not have a growth promoting effect on cotton lint yield or its biological activity was inadvertently destroyed by some unknown factor(s) before or during experimentation.